The present invention relates to automotive vehicles having an upwardly opening liftgate for providing access to the rear of the vehicle, and more particularly to a vehicle having a power-driven mechanism for opening the liftgate.
Automotive vehicles such as minivans, sport utility vehicles, or station wagons often-have a rear door attached to the vehicle by a hinge extending horizontally along the upper edge of the gate so that it has a generally vertical closed position and swings upwardly to a generally horizontal open position. Such closures are generally known as liftgates. It is known to provide a liftgate with a motorized actuation system to move the liftgate between the closed and open positions. The motorized system can be actuated by a button or switch within the passenger compartment of the vehicle and/or by a remote control unit carried by a person. Such remote control units are well known within the automotive arts, and are widely used for locking and unlocking vehicle doors.
It is known to provide an electrical control circuit for such a motorized actuator system with a safety feature that stops movement of the liftgate if it encounters an obstruction while opening or closing. U.S. Pat. No. 5,563,483 teaches a system wherein the control circuit utilizes a microprocessor, and a potentiometer is coupled to the drive motor to provide feedback to the microprocessor and causes the motor to be stopped or reversed when the motor encounters a certain degree of resistance to its movement.
While such a system may serve to prevent severe damage to the vehicle and/or the obstruction, even the amount of contact required to stop the motor may result in scratched paint and/or metal on the liftgate if it meets an obstruction. while opening or closing. Because the liftgate may overhang the rear of the vehicle by a distance of several feet when in the open position, it is not unlikely that the vehicle may be parked so closely to another vehicle, a wall, a fence, or some other obstruction that the liftgate would strike the obstruction if it were opened. The remote control opening feature of a power liftgate compounds this problem since it is possible for the person operating the remote to trigger opening of the liftgate from a position where he/she cannot adequately view the rear of the vehicle and/or its surroundings to make an informed assessment as to whether or not there is room for the liftgate to swing to the raised and open position.
It is known to provide an automotive vehicle with a reverse sensing system to alert the driver to certain objects close to the rear of the vehicle when backing up. The Ford Windstar is available with a system comprising four ranging sensors located across the rear bumper of the vehicle which transmit ultrasonic waves when the vehicle""s transmission is in reverse. The system provides an audible warning inside the vehicle when the ranging sensors detect an object within approximately six feet or less of the rear of the bumper.
It is an object of this invention to provide a liftgate actuation system in which opening and/or closing of the liftgate is inhibited if the vehicle is positioned too close to an obstruction for unobstructed movement of the liftgate.
According to one aspect of the invention, a powered liftgate actuation system is provided comprising a motor actuatable to move the liftgate between closed and open positions, a remote control unit operable to actuate the motor, at least one non-contact ranging sensor mounted to the vehicle and directed rearward to detect a clearance distance between the vehicle and an obstruction, and a control circuit for the motor operable to inhibit actuation of the motor by a remote control unit if the ranging sensor indicates the clearance distance is less than the distance by which the liftgate extends beyond the rear of the vehicle.
According to another feature of the invention, the control circuit has an override feature allowing the remote control unit to be used to actuate the motor and open or close the liftgate in spite of the ranging sensor indicating the clearance distance is too small. The override feature may be achieved by requiring that the a button on the remote control unit be held in a depressed condition for a certain length of time. Alternatively, a second actuation of the button may be required to override the inhibit feature.
According to another feature of the invention, the ranging sensor is also used as a component of a backup aid warning system used to detect obstructions located behind the vehicle while the vehicle transmission is in a reverse gear position.